US10852367B2 - Magnetic-field sensor with a back-bias magnet - Google Patents

Abstract

An embodiment of a magnetic-field sensor includes a magnetic-field sensor arrangement and a magnetic body which has, for example, a non-convex cross-sectional area with regard to a cross-sectional plane running through the magnetic body, the magnetic body having an inhomogeneous magnetization.

Description

This application is a continuation in part of U.S. patent application Ser. No. 14/290,780, entitled “Magnetic-Field Sensor,” filed on May 29, 2014, which is a division of U.S. patent application Ser. No. 12/130,678, entitled “Magnetic-Field Sensor,” filed on May 30, 2008, which claims priority to German Patent Application No. 10 2007 025 000.4, which was filed on May 30, 2007, all of which applications are hereby incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the present invention relate to a magnetic-field sensor comprising a magnet also referred to as a back-bias magnet.

BACKGROUND

In many fields of technology, magnetic-field sensors are employed to detect movements of objects, for example. In some applications, a magnetic field acting upon the magnetic-field sensor is influenced by the movement of the respective objects such that conclusions may be drawn in terms of the movement of the object on the basis of the change in the magnetic field detected by the magnetic-field sensor.

Examples are found, among others, in the field of automobile applications, the movement of wheels being monitored in the context of an ABS application (ABS=antilock system), for example, using respective magnetic-field sensors. Other applications in the field of automobile technology include observing or monitoring the movement of crankshafts, camshafts and other shafts in the field of motor vehicles.

Depending on the specific implementation of respective magnetic-field sensors, they comprise so-called back-bias magnets which are located in a fixed arrangement with regard to the actual magnetic sensor elements of the magnetic-field sensor. In such a magnetic-field sensor, the magnetic field detected by the magnetic-field sensor itself may thus be at least partly caused by the back-bias magnet. The object whose movement is to be monitored, for example, via the magnetic-field sensor, possibly influences and/or supplements, by magnets or magnetic components of its own, the bulk magnetic field which will then be detected by the magnetic-field sensor.

Depending on the technology employed in the context of the actual magnetic-field sensor elements, the back-bias magnets, which are frequently implemented as permanent magnets, have different requirements. This may be accounted for, among other things, by the fact that some magnetic-field sensor element technologies are sensitive to different magnetic-field components, exhibit different responses to magnetic fields, and comprise different magnetic-field boundaries specific to the respective type.

SUMMARY OF THE INVENTION

One embodiment of a magnetic-field sensor comprises a magnetic-field sensor arrangement and a magnetic body which comprises a non-convex cross-sectional area with regard to a cross-sectional plane running through the magnetic body, the magnetic body comprising inhomogeneous magnetization.

A further embodiment of a magnetic-field sensor comprises a magnetic-field sensor arrangement, a first magnetic body comprising a first magnetization direction, and a second magnetic body comprising a second magnetization direction, the first and second magnetization directions differing from each other.

One embodiment of a method of producing a magnetic-field sensor includes providing a magnetic body comprising a non-convex cross-sectional area with regard to a cross-sectional plane running through the magnetic body, the magnetic body having an inhomogeneous magnetization, first and second spatial areas with regard to the magnetic body existing, so that in the first spatial area, a magnetic flux density caused by the magnetic body is within a first flux density range, with regard to a predetermined spatial direction, and so that in the second spatial area, a magnetic flux density is caused by the magnetic body, with regard to the predetermined spatial direction, which is within a second flux density range, and arranging a magnetic-field sensor arrangement comprising first and second magnetic-field sensor elements, so that the first magnetic-field sensor element is arranged in the first spatial area, and the second magnetic-field sensor element is arranged in the second spatial area.

A further embodiment of a method of producing a magnetic-field sensor comprises providing a first magnetic body having a first magnetization direction, and a second magnetic body having a second magnetization direction, the first and second magnetization directions differing, a first spatial area and a second spatial area with regard to the first magnetic body and the second magnetic body existing, so that in the first spatial area, a magnetic flux density is caused by the first magnetic body and the second magnetic body with regard to a predetermined spatial direction, the magnetic flux density being within a first flux density range, and so that in the second spatial area, a magnetic flux density is caused by the first magnetic body and the second magnetic body with regard to the predetermined spatial direction, the magnetic flux density being within a second flux density range, and providing a magnetic-field sensor arrangement comprising first and second magnetic-field sensor elements, so that the first magnetic-field sensor element is arranged in the first spatial area, and the second magnetic-field sensor element is arranged in the second spatial area.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:

FIG. 1ashows a cross-sectional view of a first embodiment of a magnetic-field sensor;

FIG. 1bshows a cross-sectional view of a further embodiment of a magnetic-field sensor;

FIG. 2 shows a schematic representation of a potential example of use of an embodiment of a magnetic-field sensor;

FIG. 3aandFIG. 3bshow cross-sectional views of further embodiments of magnetic-field sensors;

FIG. 4 shows a result of a numeric simulation of a resulting magnetic fluid density in the case of an embodiment of a magnetic-field sensor and its back-bias magnet;

FIG. 5 shows a representation of an x component of the magnetic flux density in the event of the back-bias magnet shown inFIG. 4;

FIGS. 6aand 6bshow cross-sectional views of further embodiments of magnetic-field sensors;

FIG. 7 shows a result of a numeric simulation of a magnetic flux density for an embodiment of a magnetic-field sensor or of its back-bias magnet;

FIG. 8 shows a curve of x components of the magnetic flux density for the numeric simulation shown inFIG. 7;

FIG. 9 shows a magnified representation of the curves shown inFIG. 8;

FIG. 10aandFIG. 10bshow cross-sectional representations of further embodiments of magnetic-field sensors;

FIG. 11 shows a result of a numeric simulation with respect to a magnetic flux density of an embodiment of a magnetic-field sensor;

FIGS. 12aand 12bshow various curves of x components of the magnetic flux density for the numeric simulation shown inFIG. 11;

FIG. 13 shows a cross-sectional representation of a further embodiment of a magnetic-field sensor;

FIG. 14A illustrates a cross sectional view of a further inhomogeneous magnet according to the present disclosure;

FIG. 14B illustrates a spatial view of an exemplary shape of the further inhomogeneous magnet;

FIG. 14C illustrates the inhomogeneous back-bias magnet in combination with a bare die sensor;

FIG. 14D illustrates a further implementation of the inhomogeneous back-bias magnet according to the present disclosure;

FIG. 15 illustrates a B_xcomponent for an inhomogeneous and a homogeneous magnetic field;

FIG. 16 illustrates a simulated distribution of magnetization for the further inhomogeneous magnet; and

FIG. 17 illustrates simulated B_xcomponents for different angles α indicating different levels of inhomogeneous magnetization for the further magnet.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 1ato13 show schematic representations of various embodiments of magnetic-field sensors with their magnetic bodies or back-bias magnets, as well as results of numeric simulations in the form of curves and other representations. However, before giving a more detailed description of a potential application scenario of a magnetic-field sensor in the context ofFIG. 2, a description will initially be given of a first embodiment of a magnetic-field sensor along with a magnetic body or back-bias magnet in the context ofFIG. 1a.

FIG. 1ashows a first embodiment of a magnetic-field sensor100 comprising a magnetic body or back-bias magnet110 and a magnetic-field sensor arrangement120. Themagnetic body110 inFIG. 1acomprises arecess130 which faces the magnetic-field sensor arrangement120 and has a polygonal cross-section with regard to a cross-sectional plane running through the magnetic body, as is depicted inFIG. 1a.

Here, therecess130 has a polygonal cross-section with a total of seven vertices140-1 to140-7 in the embodiment shown inFIG. 1a. Unlike the cross-sectional shape of themagnetic body110 which is shown inFIG. 1a, in other embodiments of a magnetic-field sensor100, therecess130 of themagnetic body110 may also comprise a number ofvertices140 which deviates from seven. For example, in the case of a triangular recess, with respect to the respective cross-sectional plane running through themagnetic body110, same could also comprise threevertices140 only. In principle, however, any number ofvertices140 may define the respective cross-sectional shape of therecess130 with respect to the cross-sectional plane.

In terms of the extension and the shape of themagnetic body110 perpendicular to the cross-sectional plane shown inFIG. 1a, a respectivemagnetic body110 may comprise, for example, the same cross-sectional shape with regard to a cross-sectional plane which projects beyond the cross-sectional plane shown inFIG. 1aor is perpendicular to it. In other words, depending on the specific implementation of therecess130, the same shape of the recess with respect to a cross-sectional plane running through a central point or any other designated point the may result. For example, in such a case the set of allpotential vertices140 would form, with respect to a plane perpendicular to the plane shown inFIG. 1a, a circular and/or an ellipsoidal set of points, or possibly a set of points which has the shape of a partial circle or partial ellipsis.

In other embodiments of a magnetic-field sensor100, themagnetic bodies110 may exhibit other shapes of therecess130 with respect to a plane which is not the cross-sectional plane. For example, such arecess130 may comprise, with respect to a plane perpendicular to the plane shown inFIG. 1a, a cross-sectional shape deviating therefrom. Thus, it is possible, for example, for therespective recess130 being implemented in the shape of a groove within themagnetic body110, so that in this case a respective cross-section through the respectivemagnetic body110 has, for example, a rectangular shape, a square shape or any other shape which is convex.

Of course, there are other configurations of amagnetic body110 of an embodiment of a magnetic-field sensor100, wherein the respective cross-sections perpendicular to the plane shown inFIG. 1aalso have polygonal, ellipsoidal or any other cross-sectional shapes.

In addition, other configurations of amagnetic body110 magnetized in an inhomogeneous manner may naturally also be employed in embodiments of a magnetic-field sensor100. For example, with regard to the straight connectingline160 drawn in as a dotted line inFIG. 1a, and/or with regard to the non-convex cross-sectional shape generally defined herein, themagnetic body110 magnetized in an inhomogeneous manner may also take on a cross-sectional shape “to be regarded as a mirrored thereto”, as long as themagnetic body110 is magnetized in an inhomogeneous manner.

However, in the embodiments presented below, reference shall be made particularly to non-convexmagnetic bodies110 in order to simplify the description, the subsequent illustrations being applicable, however, to essentially allmagnetic bodies110 magnetized in an inhomogeneous manner.

Themagnetic body110 as is depicted, for example, inFIG. 1athus comprises a non-convexcross-sectional plane150 with respect to a cross-sectional plane running through themagnetic body110. In this context, a set of points within a plane, i.e., for example, also the cross-sectional areas such as thecross-sectional area150, is convex precisely when for any two points, respectively, of the respective quantity it is true that also the direct straight connecting line between these two points runs entirely within the respective quantity, i.e., within thecross-sectional area150. In other words, a quantity within a plane is convex precisely when all the potential straight connecting lines of all the potential points of the respective quantity run entirely within the quantity.

As was explained above, thecross-sectional area150 of themagnetic body110 is non-convex, since, for example, a straight connectingline160 drawn in as a dotted line inFIG. 1a, whose end points are both located within thecross-sectional area150, i.e., are elements of the respective quantity, however is not located entirely within the respective quantity, i.e., within thecross-sectional area150. Rather, the straight connectingline160 intersects therecess130. Thecross-sectional area150 is therefore non-convex, so that it may also be referred to as concave. The terms concave and non-convex therefore may possibly be used synonymously.

Themagnetic body110 of the embodiment of a magnetic-field sensor100 shown inFIG. 1amay be made from a permanent-magnetic material, for example. Depending on the boundary conditions on which an embodiment of a magnetic-field sensor is to be employed, i.e., not least with regard to potential temperatures of use, cost, useful magnetic fields and other parameters, themagnetic body110 may also be made, for example, from iron, cobalt, nickel or other relatively complex compounds and alloys, which possibly include the above-mentioned metals as components. In principle, respective magnetic bodies or back-bias magnets110 may be manufactured from ferrites, aluminum-nickel-cobalt (AlNiCo), also samarium-cobalt (SmCo) or neodymium-iron-boron (NdFeB). Of course, other material combinations or materials are also feasible as a field of application for the respectivemagnetic bodies110.

As is indicated inFIG. 1aby thearrows170, the magnetic body, or the back-bias magnet,110 has an inhomogeneous magnetization. The magnetization M of themagnetic body110 here has been specifically generated to be inhomogeneous, various magnetizations occurring at various points, particularly within thecross-sectional area150, which differ at least with regard to their magnitudes or intensities and/or their directions.

In other words, a magnetization of a magnetic body is inhomogeneous when it is largely not homogeneous, a homogeneous magnetization being understood to mean, in the context of the present application, a magnetization which is constant and unidirectional with regard to its direction and intensity. Put differently, themagnetic body110 has an inhomogeneous magnetization, as is shown by thearrows170, since its magnetization does not have a constant direction and/or a constant magnitude of the magnetization M, in the vectorial sense, across the entire magnetic body or across a substantial part of the entire magnetic body. In the context of the present application, a substantial portion of the entiremagnetic body110, or of themagnetic body110, is understood to mean a volume fraction of themagnetic body110 which ranges from 50% to 100%, i.e., for example, 95%, 90%, 80%, 75%, 70% or 60%, it being possible for the respective volume fractions to result as a function of the respective field of application and implementations of an embodiment of a magnetic-field sensor.

In addition, it should be noted here that for many magnets which comprise, in the entire volume, a magnetization which is constant in terms of magnitude and direction, i.e., which are magnetized in a homogeneous manner, the magnetic field resulting therefrom may be inhomogeneous both on the outside and inside of the magnet. In other words, the presence of an inhomogeneous magnetic field on the outside and/or inside of a magnet need not be an indication that the magnetization, too, is inhomogeneous. In many cases, homogeneous magnetizations are attractive particularly because they may be manufactured in a comparatively simple and inexpensive manner.

Themagnetic body110, or the back-bias magnet110, of the embodiment of the magnetic-field sensor100 as is shown, for example, inFIG. 5a, frequently comprises a remanent magnetic flux density ranging from several hundred millitesla (≥100 mT) to several tesla (3 T), depending on the example of use. Depending on the specific implementation and specification of an embodiment of a magnetic-field sensor110, themagnetic body100 may thus comprise, for example, a “magnetization” or a remanent magnetic flux density Brem of typically 500 mT or 1 T, which exists because of the magnetization. However, it should be noted in this context that the above-mentioned flux density ranges are not to be taken in a limiting sense. Rather, they are merely examples as may be used in some fields of application of embodiments of a magnetic-field sensor100. In principle, other magnetizations may be used as a function of various parameters, i.e., for example, of the technology of the individual magnetic-field sensor elements, the dimensions of the respective magnetic-field sensor, and other parameters.

In addition to the magnetic body, or the back-bias magnet,110, the embodiment of a magnetic-field sensor100 shown inFIG. 1aalso comprises the magnetic-field sensor arrangement120 comprising, for example, a substrate or achip180 and one or several magnetic-field sensor elements190 as optional components. In the embodiment shown inFIG. 1a, thesensor arrangement120 comprises at least two magnetic-field sensor elements190-1,190-2 drawn inFIG. 1a. Depending on the technology used, the magnetic-field sensor elements190 may be magneto-resistive sensor elements (xMR sensor elements), Hall sensor elements, or other sensor elements reacting to a magnetic influence, such as magnetic diodes or magnetic transistors.

With regard to the present invention, it should be noted that same may be advantageously employed particularly with such sensors or sensor elements which exhibit saturation behavior, i.e., for example, with xMR sensor elements.

By contrast, Hall probes, for example, have virtually no saturation. However, since the amplifiers connected downstream from the Hall probe exhibit saturation behavior (because the amplifier becomes saturated outside its dynamic range), it may be advantageous also with Hall probes to use the magnetic bodies described here.

The magneto-resistive sensor elements include, among others, AMR sensor elements (AMR=anisotropic magneto resistance), GMR sensor elements (GMR=giant magneto resistance), CMR sensor elements (CMR=colossal magneto resistance), EMR sensor elements (EMR=extraordinary magneto resistance), TMR sensor elements (TMR=tunnel magneto resistance), or spin-valve sensor elements. Hall sensors may be horizontal or vertical Hall sensors.

Depending on the specific implementation, the magnetic-field sensor arrangement120 may comprise further components, such as an evaluating circuit, a sensor circuit or a respective encapsulating material for protecting the individual magnetic-field sensor elements190.

In some embodiments of a magnetic-field sensor100, as is shown inFIG. 1a, for example, the magnetization M has the following symmetry conditions with regard to asymmetry line195, shown inFIG. 1a, at an x coordinate (x=0) with regard to the x component M_xof the magnetization M and to the y component M_yof the magnetization:
M_x(x)=−M_x(−x)
M_y(x)=M_y(x)  (1).

This means that the x component of the magnetization M_xhas an odd symmetry with regard to thesymmetry line195 at x=0, and that the y component M_yhas an even symmetry with regard to the x coordinate and thesymmetry line195. More generally speaking, the magnetization M in some embodiments of a magnetic-field sensor has an odd symmetry relation with regard to the associatedmagnetic body110 with respect to a component, and has an even symmetry relation with regard to another component. More specifically, in some embodiments of a magnetic-field sensor, the magnetization M of themagnetic body110 has an even symmetry relation with regard to a vector component, and has an odd symmetry relation with regard to a vector component perpendicular to the vector component.

Before further embodiments of magnetic-field sensors will be described and explained in connection withFIGS. 1bto13, it should be noted that objects, structures and components having identical or similar functional properties and features are designated by identical reference numerals. Unless explicitly stated otherwise, the descriptions of objects, structures and components having similar or identical functional properties and features may be interchanged. In addition, in the further course of the present application, summarizing reference numerals shall be used for objects, structures and components occurring several times in one embodiment in an identical or similar manner, or occurring in different figures, embodiments in a similar manner, unless features or properties of a very specific object, structure or component are explained and discussed. Utilization of summarizing reference numerals therefore enables a more compact and clearer description of the embodiments of the present invention.

FIG. 1bshows a further embodiment of a magnetic-field sensor100 which differs only marginally from the embodiment shown inFIG. 1a. The embodiment of a magnetic-field sensor100 shown inFIG. 1bagain comprises amagnetic body110, the magnetization M of which being again indicated by thearrows170. In the embodiment depicted inFIG. 1b, too, the magnetization M is inhomogeneous in a substantial portion of the magnetic body, as is shown by the course of thearrows170. More specifically, the magnetization M of themagnetic body110 again has the symmetry conditions described in connection with equation (1).

Unlike the embodiments depicted inFIG. 1a, themagnetic body110 of the embodiment of a magnetic-field sensor100 shown inFIG. 1bhas a different course with regard to an upper edge. More specifically, in the embodiment depicted inFIG. 1a, an upper edge of themagnetic body110 is delimited by a straight line, whereas in themagnetic body110 inFIG. 1b, the magnetic body extends upward beyond the area represented inFIG. 1b. Irrespective thereof, however, in the magnetic body depicted inFIG. 1b, thecross-sectional area150 is non-convex with regard to the cross-sectional plane reproduced inFIG. 1b, since the direct straight connectingline160, whose end points are located within thecross-sectional area150, again itself intersects therecess130, and thus is located within thecross-sectional area150. In other words, irrespective of the upper shape or the outer shape, thecross-sectional area150 of themagnetic body110 is non-convex irrespective of the specific shape of the outer, upper or lateral demarcation areas of themagnetic body110.

In addition, the embodiment depicted inFIG. 1bdiffers with regard to therecess130. While in the embodiment shown inFIG. 1ait has a polygonal cross-section, in the embodiment shown inFIG. 1b, the cross-section of the recess shown there is ellipsoidal.

Apart from that, the embodiments of a magnetic-field sensor100 shown inFIGS. 1aand 1bhardly differ. In the embodiment shown inFIG. 1b, a cross-section of themagnetic body110 may comprise different shapes, a similar shape or even the same shape with regard to a plane perpendicular to the cross-sectional plane shown inFIG. 1b.

In both embodiments shown inFIGS. 1aand 1b, the magnetic-field sensor arrangement120 is arranged, in relation to themagnetic body110, such that thearrangement120 is ideally also located such that is has a center of gravity or central point of the magnetic-field sensor arrangement120 on thesymmetry line195 as well. In addition, the magnetic-field sensor arrangement120 ideally is aligned, in relation to thesymmetry line195, such that a connecting line, not drawn inFIGS. 1aand 1b, of the two magnetic-field sensor elements190 shown there intersects thesymmetry line195 at right angles. In other words, the magnetic-field sensor arrangement120 ideally is arranged such that same replicates or adopts the above-described symmetry of the magnetization M of themagnetic body110. Of course, in case of real implementations of a respective embodiment of a magnetic-field sensor100, deviations may occur with respect to the shifts in the x direction and/or in the y direction and with respect to a rotation about any of these axes or any axis perpendicular to same.

As will be explained in the further course of the present application, it is this very above-described inhomogeneous magnetization M of themagnetic body110, in connection with its cross-sectional shape in some embodiments of a magnetic-field sensor while taking into account the technology used of the magnetic-field sensor elements190, that enables an improvement of an increase in the positional tolerance of the magnetic-field sensor arrangement120 with regard to themagnetic body110. In other words, in some embodiments of a magnetic-field sensor100, a larger tolerance may be achieved with respect to the precise layout of the magnetic-field sensor arrangement120 without having to accept, in subsequent operation of the embodiment of the magnetic-field sensor100, disadvantageous effects concerning accuracy of measurement, functionality or other parameters which may possibly be caused by magnetic-field sensor elements190 which are disadvantageously positioned in relation to themagnetic body110.

Especially in the case of magneto-resistive magnetic-field sensor elements190, in some embodiments of a magnetic-field sensor100 it may be advantageous to implement amagnetic body110 as is included in the framework of an embodiment. As will be explained below, in some embodiments overdriving of the respective magneto-resistive sensor elements190 may possibly be inhibited, and/or the positioning tolerance of the respective sensor elements may possibly be increased, while no or hardly any negative consequences are to be expected for the actual measuring operation.

FIG. 2 shows a typical field of use of an embodiment of a magnetic-field sensor100 in connection with determining a rotating rate, or rotating speed, of a shaft. More specifically,FIG. 2 shows an embodiment of a magnetic-field sensor100 comprising, in addition to amagnetic body110, which may be implemented as a permanent magnet, for example, and to the magnetic-field sensor arrangement120, a protective casing included in the magnetic-field sensor100. As was already explained above, the magnetic-field sensor arrangement120 additionally comprises two magnetic-field sensor elements190, which may be magneto-resistive, magnetic sensitive sensor elements, for example. As was explained above, themagnetic body110 has been drawn in a simplified manner inFIG. 2 without representing the above-explained features of the magnetic body with regard to the magnetization and the cross-section with respect to the cross-sectional plane depicted inFIG. 2. The features were not reproduced inFIG. 2 merely so as to simplify the representation.

At a distance from a plane of the magnetic-field sensor elements190, the distance being marked by anarrow200 inFIG. 2 and also being referred to as a magnetic air gap, or air gap, agenerator object210 is mounted below the embodiment of the magnetic-field sensor100, which is a toothed wheel, which sometimes also is referred to as a permeable generator wheel. Other generator objects210 include drilled wheels, magnet wheels and other round or ellipsoidal objects suited, on account of their choice of material and/or their topologies, to influence a magnetic field, which has been generated by themagnetic body110, when a movement of thegenerator object210 occurs, and possibly to generate a magnetic flux density themselves in the case of a magnet wheel.

Depending on the specific implementation and application scenario, an embodiment of a magnetic-field sensor100 may also be employed in connection with other generator objects210. For example, a respective embodiment may be employed in connection with a magnet rod, drilled rod, or rack as thegenerator object210, for example, to detect linear movement or render it detectable. In very many cases, the generator objects210 comprise a periodic structure with regard to the magnetization, the topology or other features, so that in the case of a movement of the generator objects210, a periodic change in the magnetic field (among others, that of the magnetic body110) is caused. The respective generator objects210 are frequently implemented either as part of a respective moving component, or are connected to same.

In the case of a toothed wheel as thegenerator object210, as is shown inFIG. 2, same may be coupled, for example, to a shaft, i.e., a crankshaft or a camshaft, or to a wheel. If thegenerator object210 is moved, i.e., in the case of the toothed wheel depicted inFIG. 2, is rotated, as is indicted by thearrow220, this causes a change in the magnetic field which may be detected by the magnetic-field sensor100.

Depending on the goal envisaged in the field of applying an embodiment of a magnetic-field sensor100, movements of wheels may thus be detected, for example, by means of magnetic sensors, as may be desired, for example, in the context of an ABS system. Other embodiments of a magnetic-field sensor100 may be employed, for example, in the field of engine control and monitoring, e.g., as crankshaft sensors or camshaft sensors. In this context,toothed wheels210, among others, are used in connection with small permanent magnets asmagnetic bodies110 on the rear side of the actual sensors or of the magnetic-field sensor arrangement120. Moving or rotating the wheel then results in a sinusoidal magnetic field in the area of the magnetic-field elements190, the component of the magnetic field being evaluated at the chip level, or substrate level, in the case of magneto-resistive sensors (xMR sensors). At the same time, the direction of the rotary motion of the wheel may possibly also be evaluated and detected by a further sensor or by means of other technical measures.

In many applications, a small permanent magnet is thus mounted as amagnetic body110 on a magnetic-field sensor arrangement120, so that both may be arranged before a tooth-wheel shaped permeable disk, as is schematically depicted inFIG. 2. When the disk is rotated, the teeth of thetoothed wheel210 pass the plane of the magnetic-field sensor elements190 at the distance of the magnetic air gap and thus generate a small field variation which may be detected by the embodiment of the magnetic-field sensor100 and which comprises information on the angular position and the rotating speed of the disk. In many cases, the waveform of the magnetic-field variation is nearly sinusoidal, and its amplitude drastically decreases as a function of an increasing (magnetic) air gap.

In the case of a toothed wheel as thegenerator object210, as is depicted inFIG. 2, the amplitude of the waveform frequently decreases roughly exponentially, in proportion to a ratio of the magnetic air gap and the so-called pitch (possibly multiplied by a factor of 2π). In this context, the so-called pitch is defined as the quotient of half the circumference of the toothed wheel, divided by the number of teeth if same are equidistantly distributed across the circumference of the toothed wheel. Thus, the pitch represents half the period of the toothed wheel. For this reason, it may be advisable, in some embodiments of a magnetic-field sensor100 and in various fields of application of same, to operate embodiments as close to thegenerator object190 as possible so as to bypass and to prevent, e.g., magnetic air gaps larger than approximately the width of a tooth. An increase in the magnetic air gap from about the width of one tooth to about 150% of the width of a tooth may reduce a magnetic field amplitude by more than a factor of 5, for example, depending on the specific circumstances. For example, the amplitude depends on exp(−2Pi*z/lamda), lamda being the magnetic period, i.e., lamda/2 is a width of a tooth, or a width of a gap between two teeth. If z=lamda/2 increases to z=1.5*lamda/2, the amplitude consequently will change by a factor of exp(−Pi)/exp(−Pi*1.5)=4.8.

In the case of magneto-resistive sensor elements, i.e., for example,GMR sensor elements190, it may happen that a respective magnet arrangement overdrives the individualGMR sensor elements190 with regard to the magnetic-field components in the plane of the substrate or of the chip. In such a case, it may happen that the magnetic-field sensor element(s)190 concerned will not provide any measurement signals, or measurement signals which are hardly usable.

Thus, even if, for example, thetoothed wheel210 is positioned symmetrically to the chip of the magnetic-field sensor arrangement120, i.e., if, for example, a tooth center or a gap center of thetoothed wheel210 is directly in a (xx=0) position also drawn inFIG. 2, it may happen that the flux lines of the magnet diverge, as a result of which inadmissibly large Bx components will act upon the two (magneto-resistive) magnetic-field sensor elements190 shown inFIG. 2. As was already explained in connection withFIGS. 1aand 1b, the (x=0) position here is defined by thesymmetry line195, which in connection withFIG. 2 relates to the position located precisely between the two magneto-resistive sensor elements190 shown inFIG. 2.

In such a case, both magneto-resistive sensor elements190 are driven into saturation, and can no longer give off any (usable) signal. In some applications wherein an embodiment of a magnetic-field sensor100 is employed, a common remanence of the magnetic bodies or back-bias magnets110 used is in a range of just above 1 tesla (T). Typical toothed wheels as generator objects210 comprise teeth and gaps approximately 3 mm wide, the depth of the gap also corresponding to about 3 mm. Of course, other dimensionings of respective toothed wheels or other generator objects may occur in other examples of use. Also, the respective embodiments of magnetic-field sensors100 are not limited to these values. It shall be noted in the context of the present invention that large magnetic fields at the xMR element may be achieved, for example, using large magnets or using large remanences, or using a small demagnetization factor.

Depending on the specific application, the magneto-resistive sensor elements190 are typically arranged within a range of about 1 mm before the magnet ormagnetic body110, and the toothed wheel itself is arranged about 1 to 4 mm before the magneto-resistive sensor elements190, so that the magnetic air gap is also within this range. In some applications and, thus, in some embodiments of a magnetic-field sensor100, the magnetic ormagnetic body110 has a cross-section of 5 mm in the x direction, and of 6 mm in the y direction, the magneto-resistive sensor elements190 at the chip being spaced apart by about 2.5 mm. In such a case, it may happen that the Bx component of the magnetic field strength on the right-hand one of the two magnetic-field elements190 ranges from about 95 to 117 mT, the different values resulting as a function of the (magnetic) air gap. Accordingly, in the case of a symmetric layout, Bx components ranging from −95 to −117 mT act upon the left-hand sensor element190. Depending on the specific implementation of the magnetic-field sensor element190, in particular in the case of a GMR magnetic-field sensor element, such a sensor element frequently has a linear drive range of up to +/−15 mT. If such aGMR sensor element190 is highly overdriven by the magnet, it will no longer function in a useful manner and will no longer be able to provide useful measurement signals.

With otherGMR sensor elements190 it may happen that they become saturated already at a magnetic flux density of about 10 mT. Thus, if there are magnetic-field components, or magnetic flux density components, of more than 100 mT at the location of theGMR sensor elements190, the latter will be driven into saturation, so that small superimposed alternating magnetic fields as may be caused by thegenerator object210 are no longer detectable. It may therefore be useful in such a case to reduce the above-described magnetic flux density by a factor of 15.

If, for example, merely a modulation of between 12 mT and 14 mT is caused by a tooth at a saturation field strength of about 10 mT of a GMR sensor element, the respective GMR sensor element in many cases may no longer provide a usable output signal, so that the sensor overall may no longer be able to detect the rotation of thegenerator object210.

As was already explained above, the above numerical indications in particular serve illustration and are not to be understood in a limiting sense. Embodiments of magnetic-field sensors100 may be employed within a very wide range of magnets ormagnetic bodies110, and within a very wide range of different magnetic-field sensor elements190. Also, in the case of respective application scenarios, embodiments may be combined with very many different generator objects210 so as to form speed sensors, for example, or other magnetic-based sensors.

FIGS. 3aand 3bshow two further embodiments of magnetic-field sensors100. More specifically, the two embodiments are depicted along with agenerator object210, respectively, it being possible for thegenerator object210 to be a rack or a toothed wheel, for example, which is depicted without any curvature inFIGS. 3aand 3bin order to simplify the representation.

The embodiments of magnetic-field sensors100 depicted inFIGS. 3aand 3bthus each comprise amagnetic body110 which again comprises, with respect to the cross-sectional plane shown inFIGS. 3aand 3b, a non-convex cross-section having arecess130, therecess130 being configured to be circular in the case of the embodiments shown inFIGS. 3aand 3b. Of course, it may be noted in this context that the designations circular or ellipsoidal may also be applied to respective sectors and portions of the respective geometric figures, i.e., of a circle or an ellipsis.

In the embodiments of a magnetic-field sensor100 depicted inFIGS. 3aand 3b, themagnetic bodies110, or the two back-bias magnets110, again have an inhomogeneous magnetization, as is depicted by thearrows170 in both figures. Depending on the specific implementation of an embodiment, here, too, the magnetic-field sensor arrangement120 may possibly include a casing, also referred to as a package, in addition to the chip or thesubstrate180 and the (magneto-resistive) magnetic-field sensor elements190, i.e., GMR magnetic-field sensor elements, for example.

In the embodiments depicted inFIGS. 3aand 3b, the magnet ormagnetic body110 is configured as part of a ring, and is essentially radially magnetized, as is indicated by thearrows170. More specifically, themagnetic body110 here has an annular shape, but in other embodiments of a magnetic-field sensor100, it may also have other shapes, such as that of a flat or upright ellipsis. As was already explained in the context ofFIG. 1b, it may suffice for themagnetic body110 to comprise an inner recess so that the above-described magnetization of themagnetic body110 may be performed. Basically, any outer demarcation curve desired may thus be provided, in principle. As was explained before, in some embodiments of a magnetic-field sensor100, the inner recess may be circular, ellipsoidal or polygon-shaped. In other words, in different embodiments of a magnetic-field sensor, the magnetic body may have a non-convex cross-section or a non-convex cross-sectional area in relation to a cross-sectional plane.

FIG. 3athus shows an embodiment wherein themagnetic body110 extends over 180° and is configured as an annulus. By contrast, in the embodiment depicted inFIG. 3b, themagnetic body110 depicted as an annulus extends over less than 180°. Depending on the specific implementation, themagnetic body110 may also extend over more than 180°.

The sensor IC (IC=integrated circuit), or the magnetic-field sensor arrangement120 may be moved, or shifted, both “to within the magnet” and to the area of therecess130, as is depicted inFIG. 3a. In the case of relativelysmall magnets110, or even in the case of limited design space, themagnet110 may also be placed on the back of the sensor IC, wherein a front side and a bottom side of theIC120 may be used equally well in many cases with regard to the fixing described, depending on the specific implementation of an embodiment of a magnetic-field sensor100.

However, in many cases of application it may be advisable to move theGMR sensor elements190 as close to the toothed wheel or thegenerator object210 as possible, so that it may possibly be advisable in such a case to secure themagnet110 on that side of thechip120 which contains no components (e.g. the magnetic-field sensor elements190). In such a case, it may thus be advisable to secure the magnetic-field sensor arrangement120 to themagnetic body110 such that it is rotated by 180° in relation thereto as compared to the representation ofFIGS. 3aand 3b, i.e., to secure it in a precisely inverse manner to that depicted inFIGS. 3aand 3b. The magnetic-field sensor elements190 thus may be located such that they are rotated by 180° in relation to thesubstrate180 and thegenerator object210.

Depending on the specific implementation, a typical dimension may thus comprise, in the case of embodiments as are shown inFIGS. 3aand 3b, an outside diameter of about 9 mm and an inside diameter of about 5 mm in relation to the shape of themagnetic body110. A strength of the remanent magnetization again may be higher than about 500 mT or higher than about 1 mT, depending on the specific implementation of an embodiment.

In some embodiments, the spacing between the twosensor elements190 is about the size of a tooth or a tooth gap of agenerator object210. In some embodiments, or in some cases of application, this may be, for example, 2.5 mm for the distance between the two outer sensor elements shown inFIGS. 3aand 3b. Depending on the specific implementation, a central sensor element may be employed, for example, for detecting the direction, it being possible for the central sensor element to be arranged in the center between the left-hand and right-hand sensor elements. However, in some fields of application, other distances between thesensor elements190 are useful. Other distances, for example 1.7 mm, may also be used.

The surface of thechip180 in many cases is arranged at a distance before themagnet110 ranging from about 0.5 mm to about 2 mm, distances of about 0.7 mm frequently representing a useful compromise, since on the one hand, themagnet110 should be located as close as possible to thechip180, and thus, to themagnet wheel210 and, on the other hand, a thickness of mounting components (package bottom, lead-frame thickness, die-attach thickness, and silicon thickness) frequently is in a range of about 0.7 mm. A distance of thechip180 from thegenerator object210, also referred to as an air gap, may amount to several tenths of a millimeter as a minimum, but as a maximum should not exceed a spacing of the width of about four teeth or four tooth gaps in some fields of application, since with larger air gaps, the magnetic field signal amplitude will decrease exponentially.

FIG. 4 shows a result of a numerical simulation of a magnetic field strength curve and of magnetic field lines as result in the case of amagnetic body110 as is described in the context ofFIG. 3aand the embodiment discussed there. Calculating magnetic fields, as have caused, for example, the magnetic field curve shown inFIG. 4, in many cases is anything but trivial and basically comes down to solving the four Maxwell differential equations for electromagnetic fields. There are indeed simplified forms for special cases, which possibly may be solved in a closed form, but specifically for calculating magnetic fields, magnetic flux densities and other curves and characteristics discussed in the context of the present application, numeric simulation, which may be performed, for example, on the basis of a two-dimensional or three-dimensional simulation using the finite elements method is generally indispensable. Respective simulations and calculations may be performed, for example, on the basis of the equation

$\begin{array}{cc}B={\mathrm{<figure-callout\; label="\mu "\; filenames="US10852367-20201201-D00001.png,US10852367-20201201-D00002.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_0{\int }_v\frac{{\mathrm{redMxdegrees}}_A\mathrm{<figure-callout\; label="r"\; filenames="US10852367-20201201-D00005.png,US10852367-20201201-D00008.png"\; state="\{\{state\}\}">r</figure-callout>}}{4\pi {\mathrm{<figure-callout\; label="r"\; filenames="US10852367-20201201-D00005.png,US10852367-20201201-D00006.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\mathrm{dV},& \left(2\right)\end{array}$
while taking into account the respective boundary conditions, B being the magnetic induction or the magnetic flux density as a vectorial quantity, μ0 designating the permeability of the vacuum, red M designating the rotation of the (vectorial) magnetization, degreeA r designating the gradient of the positional coordinate with regard to the starting point A, and r being the distance between the starting point and the source point. Integration is performed across the entire space, i.e. not only within the material of themagnetic body110, but also across its surface, which is indicated by the “integration boundary” V in equation (2).

In addition to themagnetic body110,FIG. 4 also schematically depicts thegenerator object210 shown inFIGS. 3aand 3b. In addition to a multitude offield lines230, for some areas, the respective magnetic flux density of between 0.2 T to a maximum of 0.5 T is additionally depicted inFIG. 4. Here, anarrow240 in the inner part of the representation inFIG. 4 marks a decrease of the magnetic field strength as is depicted by anarrow250 in the area of the legend.

FIG. 4 thus represents the cross-section of the magnetic body in the form of an annulus extending over 180° and being magnetized in the radial direction, as was already described in connection withFIG. 3a. The toothed wheel as thegenerator object210 here is positioned symmetrically to themagnet110. In this position, the Bx component of the magnetic flux density at the location of the magnetic-field sensor elements190 (not shown inFIG. 4) should ideally be as close to zero as possible, but at least within the linear control range of a GMR sensor element, i.e., for example, between approx. −15 mT and +15 mT.

The result, shown inFIG. 4, of a numeric simulation is based on, with regard to themagnetic body110, a remanence of 1 T of themagnetic body110, the remanence extending homogeneously across the entiremagnetic body110 in terms of magnitude. However, the direction of the magnetization, which due to its radial nature is inhomogeneous, is exempt therefrom.

In addition,FIG. 4 hashorizontal lines260 drawn in between the end faces of the magnet, in the area of thelines260, the magnetic field strength Bx having been evaluated as a function of the x coordinate in the context of the curves represented inFIG. 5 which follows.

FIG. 5 depicts a total of eleven curves270-1 to270-11 reproducing the magnetic flux density Bx in tesla (T) for thelines260 represented inFIG. 4. The curves270 here correspond, in an ascending order, to their numbers which are indicated after the hyphen in the context of the reference numerals, to the y positions y=−0.5 mm, −0.4 mm, −0.3 mm, −0.2 mm, −0.1 mm, 0 mm, +0.1 mm, +0.2 mm, +0.3 mm, +0.4 mm, +0.5 mm.

The curves270 show that due to the symmetry of the arrangement, the x component of the magnetic flux density Bx versus the x coordinate x almost vanishes for the case of y=0 (curve270-6), and thus would represent a basically ideal position for the GMR sensor elements. If, for example, the magnetic-field sensor elements190 are positioned such that they are symmetrically distributed around x=0 at a distance of 1.25 mm, i.e., at the x positions x=+/−1.25 mm, y positions ranging from y=−0.1 mm to y=+0.1 mm are quite suited to ensure x components of the magnetic field strength of, in terms of magnitude, less than 20 mT (|Bx|<20 mT), as the curves270-5,270-6,270-7 for the y positions y=0.1 mm, 0 mm, +0.1 mm show. The curves270 essentially comprise a mirror symmetry with regard to the point (x, Bx)=(0 m, 0 T). As compared to a simple cubic magnet having a continually homogeneous magnetization, a reduction of the x component of the magnetic flux density Bx may thus be achieved by employing an embodiment of a magnetic-field sensor100, it sometimes being possible for the reduction to amount to as much as one order of magnitude.

FIGS. 6aand 6bshow further embodiments of a magnetic-field sensor100 which are similar to the embodiments ofFIGS. 3aand 3b, but differ from same in that themagnetic bodies110 are magnetized in an azimuthal manner, as is indicated by thearrows170. With this possibility of an embodiment of a magnetic-field sensor100, themagnetic body110 may, as is depicted, for example, inFIG. 6a, comprise an annular cross-section extending over 180° C. Likewise, as is depicted inFIG. 6b, it may comprise a cross-section extending over less than 180°. Themagnet110 of the embodiment shown inFIG. 6bmay therefore be regarded as “cut off in the radial direction”, other shapes of themagnetic body110 being also possible, of course. For example,magnetic bodies110 wherein the end faces are cut off, for example, in the x direction or in the y direction are also conceivable. As was already explained above in the context ofFIGS. 1a, 1b, 3a, and 3b, the outer shape of the magnetic body is less decisive in this context. Therefore, other directions which are oblique to the above-mentioned directions are also possible as “sectional directions” of themagnetic body110.

Apart from the magnetization M as is depicted by thearrows170 inFIGS. 6aand 6b, the embodiments of a magnetic-field sensor100 which are shown in the figures hardly differ, or do not differ at all, from the embodiments shown inFIGS. 3aand 3bin terms of the further components. For this reason, reference shall be made, particularly with respect to the further components, to the respective descriptions thereof.

The magnetization of themagnetic body110 as is depicted inFIGS. 6aand 6bthus obeys the following symmetry conditions with respect to the x component M_x(x) and the y component M_y(x):
M_x(x)=M_x(−x)
M_y(x)=−M_y(−x)  (3).

This means that in this case the x component of the magnetization has an even symmetry relation with respect to the symmetry line195 (x=0), whereas the y component of the magnetization in this case meets an odd symmetry relation with respect to x. In this case, too, it may be stated in some embodiments of a magnetic-field sensor100 that one of the two magnetization components M_xand M_ymeets an odd symmetry relation with regard to x, whereas the other meets an even symmetry relation with regard to the x coordinate.

FIG. 7 shows a representation of a result of a numeric simulation which is based on amagnetic body110 comprising an extension of more than 180° and being magnetized in the azimuthal direction, the magnitude of the magnetization being set to be constant across the volume of themagnetic body110. In other words, the results of the simulation shown inFIG. 7 are based on an embodiment of a magnetic-field sensor comprising amagnetic body110 magnetized in the azimuthal direction at a constant magnitude, so that the magnetization again is inhomogeneous due to the changing direction of same. Here,FIG. 7 again shows a plurality offield lines230 as well as anarrow240 in the inner part of the representation which corresponds to a direction along a decreasing magnetic flux density ranging from 0.5 T to 0.2 T, as is also indicted by thearrow250. In addition,different lines260 are again drawn inFIG. 7, which relate to the curves270 reproduced inFIGS. 8 and 9. In other words, within the context of the followingFIGS. 8 and 9, suitability of thedifferent lines260 with regard to a potential position for the magnetic-field sensor elements190 is examined.

FIG. 8 shows curves270-1 to270-8 of the x component of the magnetic flux density Bx as a function of the x coordinate for different y coordinates. More specifically, the curve270-1 here corresponds to a y coordinate of y=−0.8 mm, the y coordinate being reduced by 0.1 mm in each case as numeral of the respective curve increases, the curve being reproduced after the hyphen in the context of the reference numeral. Consequently, the curve270-2 corresponds to a y coordinate of y=−0.9 mm, and, for example, the curve270-8 corresponds to a y coordinate of y=−1.5 mm. Here,FIG. 8 initially shows the respective curves270 on a coarse scale in a range from x=−2 mm to x=+2 mm, whileFIG. 9 represents a magnification of the represented range from about x=1.0 mm to x=1.85 mm.

Thus,FIG. 8 initially shows that almost independently of the y parameter selected in each case, in the range from about x=1.3 mm and x=1.4 mm, all curves270 have an x component of the magnetic flux density Bx which ranges from about +/−(20 mT-40 mT). At a smaller distance from the magnet ormagnetic body110, i.e., for higher y values, the curves270 in the range of around x=+/−1.4 mm run through the B_x=0 line, so that this may represent quite a suitable location for magneto-resistive sensor elements190, i.e.,GMR sensor elements190, for example.

Accordingly, inFIG. 9, the range of the curves depicted inFIG. 8 is represented in a magnified manner in the range of around x=1.4 mm. For example,FIG. 9 shows that in particular the curves270-2,270-3 and270-4, which correspond to the y parameters y=−0.9 mm, −1.0 mm and −1.1 mm, intersect the “Bx=0” line in the range of around x=1.4 mm, as is shown by the detailed image inFIG. 9.

Before further embodiments of a magnetic-field sensor100 will be described in the context ofFIGS. 10aand 10b, a short outline shall be given of a method with which the inhomogeneous magnetizations discussed in the preceding figures may be realized. In the case of themagnetic bodies110 which comprise radial or quasi-radial magnetizations, as are shown, for example, inFIGS. 1a, 1b, 3a, and 3b, a counterpart which is suitably shaped and made of iron, for example, may be inserted into therecess130 of the respective magnetic body, the counterpart seamlessly adjoining the surface, suitably shaped, of themagnetic body110. Also, an iron part, suitably shaped, may be placed into the outer surface from the outside, so that the futuremagnetic body110 is covered by respective iron parts from the outside and the inside. Subsequently, the two iron parts may be interconnected by a clamp which may take on almost any shape desired. A winding may be wound around the clamp, the winding having current applied thereto in order to generate the magnetization.

In the case of a magnetic body having an azimuthal magnetization, a circular conductor may be placed inside the magnet, i.e., into therecess130 of themagnetic body110, and a circular conductor may be fit snuggly, ideally seamlessly, to themagnetic body110 on the outside. If a current flowing in the inner metallic conductor is sent out of the drawing plane drawn inFIG. 6aandFIG. 6b, respectively, and if in the outer conductor, a corresponding current is sent into the drawing plane, the respective magnetization within themagnet110 will be aligned in the azimuthal direction in an anticlockwise manner.

FIGS. 10aand 10bshow further embodiments of a magnetic-field sensor300 differing from the above-shown embodiments of respective magnetic-field sensors100 in that the embodiments shown here comprise a firstmagnetic body310 and a secondmagnetic body320, the firstmagnetic body310 comprising a first magnetization direction which is characterized by anarrow330 inFIGS. 10aand 10b, respectively. Likewise, the secondmagnetic body320 has a magnetization direction plotted by anarrow340 inFIGS. 10aand 10b, respectively. The two magnetization directions of the twomagnetic bodies310,320 differ from each other and form an angle with each other.

With regard to asymmetry line195, which again corresponds to an x coordinate of x=0, the magnetization directions (arrows330,340) of the twomagnetic bodies310,320 each form an angle with thesymmetry line195 which is identical, in terms of magnitude, for the twomagnetic bodies310,320, or which does not deviate from one another by more than typically 20°, 10°, 5° or 2°, depending on the specific implementation of a respective embodiment of a magnetic-field sensor300 and its specifications. In other words, the twomagnetic bodies310,320 in many embodiments of a magnetic-field sensor300 comprise a symmetrical magnetization with regard to thesymmetry line195.

In addition, the embodiments of a magnetic-field sensor300 depicted inFIGS. 10aand 10bagain each comprise a magnetic-field sensor arrangement120 having asubstrate180 and one or more magnetic-field sensor elements190. As was already described in connection with the above-explained embodiments of a magnetic-field sensor100, the magnetic-field sensor arrangement may comprise a single magnetic-field sensor element190 or a plurality of respective magnetic-field sensor elements190. In the embodiments shown inFIGS. 10aand 10b, the magnetic-field sensor arrangement120 in each case comprises two magnetic-field sensor elements190 arranged essentially symmetrically to thesymmetry line195 which are manufactured by means of, for example, the potential magnetic-field sensor element technologies already discussed above. In this case, too, the magnetic-field sensor elements may include Hall sensor elements, magneto-resistive sensor elements, or other corresponding magnetic-field sensor elements.

It should be noted in this context that because of the above-described problems of the positioning tolerance in the case of real implementations of embodiments of magnetic-field sensors100,300, the above-described symmetry properties of the various components may deviate, with regard to thesymmetry line195, only within a predefined tolerance limit, i.e., for example, within a positioning tolerance, which is dependent on the application, in the lateral direction or in the vertical direction. In other words, if thesymmetry line195 relates to a center of, e.g., two magnetic-field sensor elements190 on thesubstrate180 of the magnetic-field sensor arrangement120, the twomagnetic bodies310,320, which together form the back-bias magnet may possibly deviate from their respective positions within predefined positioning tolerances. In many cases, the respective positioning tolerances are application-specific and are certainly influenced, for example, by the technology of the magnetic-field sensor elements190 used.

In addition, agenerator object210 is again drawn inFIGS. 10aand 10b, thegenerator object210 again being, for example, a rack, a magnet rod, a drilled rod, a toothed wheel, a drilled wheel, or a magnet wheel. Depending on the specific application, other generator objects210 may also be employed, it possibly being useful in many cases, depending on the specific implementation, to configure therespective generator object210 such that it is able to cause a modulation, for example, a periodic or sinusoidal modulation, of a magnetic field which (among others) is generated, in this case, by the firstmagnetic body310, frequently configured as a permanent magnet, and the secondmagnetic body320 of the back-bias magnet arrangement, or of the back-bias magnet.

With respect to thesymmetry line195, in many embodiments of a magnetic-field sensor300, the firstmagnetic body310 and the secondmagnetic body320 are configured, or arranged, to be symmetrical to same. In addition to the above-mentioned possibility of performing a definition of thesymmetry line195 with regard to a central position of magnetic-field sensor elements190, if same are present in a corresponding number and layout, there is naturally also the possibility of defining thesymmetry line195 with regard to a central point or any other corresponding line or mark with respect to thesubstrate180. While taking into account the positioning deviations or positioning tolerances of the individualmagnetic bodies310,320 which are caused, for example, by manufacturing tolerances, they each have a symmetrical installation position with regard to thesymmetry line195.

As was explained before, depending on the specific definition of the location of thesymmetry line195, the twomagnetic bodies310,320 and/or the locations of the individual magnetic-field sensor elements190 may comprise corresponding installation tolerances or positioning tolerances with regard to thesymmetry line195. In other words, a center of gravity of the twomagnetic bodies310,320 may be spaced apart from thesymmetry line195 by a distance typically smaller than a corresponding positioning tolerance.

The same applies not only in the x direction, but also in the y direction, which is perpendicular thereto, as is drawn inFIGS. 10aand 10b. Depending on the production technology used, in particular on the technology of securing the magnetic bodies with regard to the magnetic-field sensor arrangement120, positioning errors ranging from several 100 μm to several millimeters thus cannot occur in the x direction and/or y direction as well as in the z direction, which is not shown inFIGS. 10aand 10b. In other words, the respective positioning tolerances may be in the range of up to several 100 μm, or in the range of up to several millimeters, i.e., in the range of up to about 1000 μm, or in the range of up to about 2 mm.

With regard to the positioning of the individual magnetic-field sensor elements190 in relation to one magnetic body, respectively, of the twomagnetic bodies310,320, in many embodiments of a respective magnetic-field sensor300, provided that the magnetic-field sensor elements190 and/or of themagnetic bodies310,320 are arranged symmetrically, the magnetic-field sensor elements190 each comprise x coordinates within the range of the x coordinates of one of the twomagnetic bodies310,320. In other words, in such embodiments of a magnetic-field sensor300, the associated magnetic-field sensor elements190 are located above or below the respectivemagnetic bodies310,320.

With respect to the angles formed by the magnetization directions of the individualmagnetic bodies310,320 and thesymmetry line195, or theline350 extending perpendicular to same and also drawn inFIGS. 10aand 10b, in many embodiments of a magnetic-field sensor300, an angle of the magnetization of one of the twomagnetic bodies310 in many cases forms an angle of between 10° and 80° in terms of magnitude with thesymmetry line195. In many embodiments of a magnetic-field sensor300, thesymmetry line195 runs perpendicular to a main surface or surface of thesubstrate180 having the magnetic-field sensor elements190 arranged thereon. Accordingly, the respective magnetizations also form an angle, with regard to theline350, ranging from 10° to 80° in terms of magnitude. In addition, in the case of a symmetric design of the twomagnetic bodies310,320, the respective magnetizations in each case form an angle with each other which ranges from 20° to 160° in terms of magnitude. Depending on the specific field of application, other ranges of angles, which shall be explained in more detail in the further course of the present application in the context of numeric simulations, may also occur in embodiments of a magnetic-field sensor300.

The embodiments of a magnetic-field sensor300 depicted inFIGS. 10aand 10bdiffer essentially with respect to the arrangement of the twomagnetic bodies310,320 in relation to each other. While in the embodiment shown inFIG. 10a, the twomagnetic bodies310,320 immediately adjoin each other, for example, in that they are fixed to each other by means of gluing, in the embodiment shown inFIG. 10b, the twomagnetic bodies310,320 are separated from each other by a respective gap. The gap between the twomagnetic bodies310,320 may be filled, for example, with a magnetic or non-magnetic material, which serves, for example, for attachment or serves the overall architecture of the embodiment of a magnetic-field sensor300. For example, a plastic attachment may be partly or fully inserted between the twomagnetic bodies310,320, to which plastic attachment the twomagnetic bodies310,320 are glued or otherwise attached. Alternatively or additionally, the twomagnetic bodies310,320 may also be fixed to one another within the framework of the overall installation of the magnetic-field sensor arrangement120, so that encapsulating material at least partly enters into the gap between the twomagnetic bodies310,320.

As was already set forth in the context of the embodiment shown inFIGS. 3a, 3bof a magnetic-field sensor100, in embodiments of a magnetic-field sensor300, too, the magnetic-field sensor arrangement120 with itssubstrate180 and the magnetic-field sensor elements190 may, for its part, comprise a package.

Of course, it is also possible, in principle, that no solid material is inserted between the twomagnetic bodies310,320, as is shown inFIG. 10b, but that rather the twomagnetic bodies310,320 are directly connected or glued to the magnetic-field sensor arrangement120. In such a case, introducing a material between the twomagnetic bodies310,320 may possibly be dispensed with.

In the embodiments of a magnetic-field sensor300 which are shown inFIGS. 10aand 10b, two individual magnets asmagnetic bodies310,320 are assembled to form a new magnet or back-bias magnet such that, again, the symmetry conditions given in equation (1) apply to the magnetization components of the overall arrangement of the two magnetic bodies. This, too, again corresponds to an inhomogeneous (bulk) magnetization with respect to the overall arrangement of the twomagnetic bodies310,320. More specifically, this corresponds to an inhomogeneously magnetized bulk magnet, each half of the volume of which consists of one homogeneously magnetized magnetic body, or one homogeneous area, respectively. InFIGS. 10aand 10b, in the embodiments of a magnetic-field sensor which are shown there, a second cube is joined with an oblique magnetization, respectively, as possibly the simplest example.

Depending on the specific implementation, for example, the twomagnetic bodies310,320 may be configured as two block magnets having a width of about 2 mm and a height of about 5 mm, and may be bonded to one another back to back. Both individualmagnetic bodies310,320 in this context are homogeneously magnetized, a remanence of about Brem=1 T prevailing in the respective direction shown by the magnetization, or thearrows330,340, again depending on the specific implementation. In some embodiments, the magnetization direction may comprise, for example, an angle of +/−50° with respect to thesymmetry line195, i.e., to the vertical direction.

Some embodiments of a magnetic-field sensor300, which correspond to the arrangements ofFIGS. 10aand 10b, provide very good results with regard to a combination with a magnetic-field sensor arrangement comprising magneto-resistive sensor elements. In addition, they may frequently be manufactured in a particularly simple manner since the respectivemagnetic bodies310,320 as homogeneously magnetized individual magnets may be manufactured in a comparatively simple manner.

As it was the case already in the context of the embodiments of a magnetic-field sensor300 which are shown inFIGS. 3aand 3b, it may also be useful in this case, depending on the specific implementation, to implement the magnetic-field sensor arrangement120 such that it is mirrored with respect to theline350, so that the magnetic-field sensor elements190 in connection with the finished magnetic-field sensor face thegenerator object210.

As is schematically depicted inFIG. 10b, the twomagnetic bodies310,320 may also be spaced apart from each other by a non-magnetic gap. Depending on the specific implementation, this may be helpful in installation, for example, since a corresponding distance may be configured as an adhesive surface. In addition, there is also the possibility of influencing an interaction of the twomagnetic bodies310,320 by introducing such a non-magnetic gap, so that they may not superimpose or influence each other to such a large degree.

Thus, some embodiments of a magnetic-field sensor300 with regard to the back-bias magnet formed by the twomagnetic bodies310,320 are based on the idea that when the field lines of a magnet diverge, a second magnet may be arranged next to it, the second magnet canceling out the undesired components of the first magnet.

FIG. 11 shows a result of a numeric simulation of a magnetic flux density distribution of an embodiment of a magnetic-field sensor300 as is schematically shown inFIG. 10a. In addition to a number offield lines230,FIG. 11 shows a magnetic flux density distribution calculated in the area of the twomagnetic bodies310,320 and ranging from 0.2 to 0.5 T. As is already schematically shown inFIG. 10a, the twomagnetic bodies310,320 have a magnetization having a magnetic remanence of Brem=1 T, which is also indicted by thearrows330,340 inFIG. 11. The magnetic flux density distribution resulting therefrom is reproduced in accordance with the gray scale distribution depicted inFIG. 11, a maximum magnetic flux density prevailing at a contact area of the twomagnetic bodies310,320, while a magnetic flux density clearly smaller than same prevailing outside the twomagnetic bodies310,320.

In addition,FIG. 11 depicts aline260, with respect to whichFIG. 12ashows an x component of the magnetic flux density Bx in a range from x=−2 mm to x=+2 mm for a y coordinate of y=−1 mm. Here, the numeric simulation shown inFIG. 11 is based on two cubic magnets ormagnetic bodies310,320 each having a homogeneous magnetization which, however, forms an angle of +/−35° with the y or By axes extending vertically downward. Consequently, there is an angle of 55°, in terms of magnitude, between the two magnetizations of the twomagnetic bodies310,320 and the horizontal.

As was briefly indicated above,FIG. 12ashows the x component Bx as a function of the x coordinate for a y value of y=−1 mm, which corresponds to theline260 shown inFIG. 11. Subsequently,FIG. 12bshows the corresponding x components of the magnetic flux density Bx as a function of the x coordinate foray value of y=−1.5 mm, which is not drawn inFIG. 11, however.

In the event of a y value of y=−1 mm,FIG. 12ashows the x component of the magnetic flux density Bx in the range from x=−2 mm to x=+2 mm for various angles of the magnetizations of the twomagnetic bodies310,320. Here, the simulations are based on the above-explained symmetry of the magnetization directions of the twomagnetic bodies310,320, each of which forms an angle, in terms of magnitude, with the horizontal in each case, the angles being reproduced using the reference numerals of the individual curves270. The curve270-70 is based on an angle of 70° of the magnetizations of the twomagnetic bodies310,320 with the horizontal, so that for this simulation or calculation, the magnetizations of the two magnetic bodies form an angle of 20° with thesymmetry line195 ofFIG. 10a. Accordingly, the curve270-55 corresponds to the case shown inFIG. 11 of an angle of 35° between thevertical symmetry line195, or to an angle of 55° of the magnetization and the horizontal.

Accordingly,FIG. 12bshows several curves270 for angles ranging from 40° to 70°, which are formed by the magnetizations of the twomagnetic bodies310,320 and the horizontal. Consequently, the curves270-40 to270-70 depicted inFIG. 12bcorrespond to angles ranging from 20° (curve270-70) to 50° (curve270-40) of the magnetizations of themagnetic bodies310,320 with respect to thevertical symmetry line195 shown inFIG. 10a. Especially in the case, shown inFIG. 12b, of a vertical distance of 1.5 mm of the magnetic-field sensor elements190 from the lower edge of the twomagnetic bodies310,320 (y=−1.5 mm; the magnet ends at y=0 mm), it may be seen that the condition |Bx|<20 mT may be met for further ranges of the x coordinates in the case of y=−1.5 mm. Since this may also be met for the case shown inFIG. 12ain the range of further x coordinates, there is thus the possibility, in particular, of implementing magneto-resistive magnetic-field sensor elements190 using an embodiment of a magnetic-field sensor300 as is schematically shown, for example, inFIG. 10aor10b, without the magnetic-field sensor elements190 being driven into saturation by the respective x components of the magnetic fields caused by themagnetic bodies310,320.

In other words, using an embodiment of a magnetic-field sensor300, a horizontal component of a magnetic flux density (for example, x component) Bx may be created within a comparatively wide range of x and y coordinates, the component not causing a saturation of magneto-resistive sensor elements190. In the case of GMR sensor elements,FIGS. 12aand 12bthus show that a condition |Bx|<20 mT, which applies to many GMR sensor elements, may be met for wide ranges of x and y coordinates.

In addition,FIGS. 12aand 12bshow that by varying the directions of the twomagnetic bodies310,320, the respective ranges may be shifted such that different distances may be realized between magnetic-field sensor elements190. Thus, it is possible to provide different embodiments of magnetic-field sensors300 having different mutual distances of the magnetic-field sensor elements190.

In summary, one may state that by using corresponding embodiments of magnetic-field sensors300 comprising (at least) twomagnetic bodies310,320, magnetic systems may be built, so that the respective magnetic-field sensor elements190 are not driven into saturation even in the case of sensitive magneto-resistive sensor elements, i.e., GMR sensor elements, for example.

FIG. 13 shows a further embodiment of a magnetic-field sensor300 which differs from the embodiments, shown inFIGS. 10aand 10b, of a magnetic-field sensor300 essentially in that the twomagnetic bodies310,320 no longer comprise, with respect to their geometric shapes, an oblique magnetization, but rather are perpendicularly magnetized with respect to a front face. In this case, the twomagnetic bodies310,320 are no longer arranged in parallel with respect to their side faces, as was the case in the embodiments inFIGS. 10aand 10b. Rather, in order to achieve the two different magnetization directions of the twomagnetic bodies310,320, they are now arranged, for their part, at a respective angle with respect to thesymmetry line195 or to theline350 perpendicular to same.

Thus, in this case, too, the firstmagnetic body310 and the secondmagnetic body320 comprise differing first and second magnetization directions, respectively. Thus, an inhomogeneous bulk magnetization is achieved, also in the case of such an arrangement ofmagnetic bodies310,320, by superimposing the magnetic fields of the two (homogeneously magnetized)magnetic bodies310,320.

In other words, respective arrangements ofmagnetic bodies310,320 comprising different magnetization directions, respectively, may be found by employing two cubic magnets or magnetic bodies which are magnetized in the longitudinal direction and are implemented and installed such that they are tilted by a respective angle, e.g., +/−35°, relative to the y axis, instead of using two slanted or oblique magnetizedmagnetic bodies310,320. In other words, for embodiments of magnetic-field sensors300 it is irrelevant whether the two different magnetization directions of the twomagnetic bodies310,320, as are represented by thearrows330 and340, are created by using magnetic bodies comprising different, slanted magnetizations, or whether magnetic bodies comprising identical magnetizations are employed, which, however, are built in an accordingly slanted manner or using corresponding installation directions within the context of the respective embodiment of the magnetic-field sensor300.

With regard to the more specific installation positions of the individualmagnetic bodies310,320 in an embodiment as is depicted inFIG. 13, the above explanations shall also apply, of course, the only difference being, in this case, that the respectivemagnetic bodies310,320 now is rotated accordingly.

Actually, there is a very large degree of freedom with regard to the specific shapes of the individualmagnetic bodies310,320. In principle, any shapes conceivable of respective magnetic bodies may be used. For example, cubic, cylindrical and other magnetic bodies, for example, magnetic bodies which taper off, are feasible. In addition, of course, not only homogeneously magnetized magnetic bodies may be used in the context of the twomagnetic bodies310,320, as was implicitly assumed in the embodiments previously described, but use may naturally also be made of inhomogeneously magnetized magnetic bodies. In other words, themagnetic bodies310,320 may also be implemented inhomogeneously with regard to their magnetization directions and their magnetization intensities.

Embodiments ofmagnetic field sensors100,300 thus enable to reduce horizontal magnetic-field components, or horizontal components, of the magnetic flux density by using inhomogeneous magnetization of themagnetic body110, or of the back-bias magnet, the latter including at least the twomagnetic bodies310,320, to such a degree that, for example, magneto-resistive sensors (xMR sensors) are no longer overdriven, i.e., driven into saturation. As was already explained above, embodiments of magnetic-field sensors100 therefore enable to reduce the flux density component, which in the context of the present application is casually also referred to as the Bx field of the back-bias magnet, by means of the inhomogeneous magnetizations described to such a degree that respective overdriving of the sensors or sensor elements will not occur.

Embodiments of the present invention in the form of magnetic-field sensors100,300 achieve a field line curve desired in that, among other things, the respective components of the resulting magnetic flux density are limited by an inhomogeneous magnetization of themagnetic bodies110,310,320. Accordingly, embodiments of magnetic-field sensors100,300 may possibly also be produced without implementing magnetic bodies with extremely filigree shapes or recesses, or respective embodiments of magnetic-field sensors100,300 may possibly also be developed and built without using highly permeably parts as magnetic lenses for field-line deformation. Embodiments of respective magnetic-field sensors100,300 may be used, among other things, for magneto-resistive speed sensors while employing respective back-bias magnet circuits in the form of themagnetic bodies110,310,320. Examples of use of respective embodiments of magnetic-field sensors are found in the automobile sector as well as other sectors, such as mechanical engineering, plant engineering, aircraft construction, shipbuilding, and other fields of technology where magnetic fields need to be detected.

FIG. 14A illustrates a cross-sectional view of a further embodiment of aninhomogeneous magnet400 suitable as a back-bias magnet to be used in combination withmagnetic sensor120 as discussed above. Theinhomogeneous magnet400 is somewhat similar to themagnet110, or themagnetic bodies310,320. It is to be noted however that theinhomogeneous magnet400 does not comprise two distinct magnetic bodies of substantially homogeneous magnetization that are joined together or meet under a specific angle leading to the above described degree of inhomogeneous magnetization. To the contrary, theinhomogeneous magnet400 is moldable as a unitary member, yet comprising the inhomogeneous magnetization as indicated by the arrows14-1,14-2,14-3 representing a direction of magnetization at a certain position within the cross-sectional view of themagnet400. The cross sectional view ofFIG. 14A is shown along the x-z plane this is to say a B_xcomponent of the magnetization is indicated at the bottom of the figure, while a B_zcomponent of the magnetization is indicated to the left side of the figure. It will be appreciated that this choice serves illustrative purposes and themagnet400 may comprise an inhomogeneous magnetization within other cross-sections instead. The magnetization illustrated inFIG. 14A is depicted symmetrical to a symmetry line14-0 as represented by the dot dashed line.

While the inhomogeneous magnetization ofFIG. 14A is illustrated as being fully symmetrical to the symmetry line14-0, it will be appreciated that for a real cross-section of theinhomogeneous magnet400 various effects may break symmetry of the magnetization within the cross-section, so that this magnetization is no longer fully symmetrical. Such effects may be faces limiting themagnet400, (magnetic) impurities within themagnet400, and/or magnetic substances sufficiently close to the magnet but are not limited thereto. For the present disclosure a magnetization shall be considered symmetrical within a cross-section even if only 90%, 80% or 50% of the cross-sectional area in fact exhibit a symmetrical magnetization with regards to the symmetry line14-0 within the cross-section.

For this disclosure the magnetization (as illustrated inFIG. 14), it is to be understood that this symmetry line14-0 may be indicating a mirror symmetrical magnetization of themagnet400. Without limitation the symmetry line14-0 as indicated in the cross-section ofFIG. 14A, may be indicating higher order symmetry of themagnet400, say a three-fold or higher order of symmetry. An object of higher order of symmetry comprises more than one cross-sectional plane to which or within which some properties of the object are symmetrical, say for example a magnetization of the object or crystal structure of a mineral. So for a higher order symmetry line there may more than one cross-section present to which or within which the property of the symmetrical object is symmetrical, while the more than one cross-sections actually intersect at the higher order symmetry line.

It will further be appreciated that the symmetry line14-0 of themagnet400 as displayed inFIG. 14A may in fact be indicating a rotational or an ellipsoidal symmetry axis. So a person of ordinary skill will readily appreciate that the back-bias magnet400 may also be of rotational symmetry. Therefore, any disclosure pertaining to the inhomogeneous (back-bias) magnet, such as back-bias magnet400, may be transferred to objects of rotational symmetry. A rotational or ellipsoidal symmetry of the magnet may be of interest depending on circumstances. It will be appreciated that an ellipsoidal symmetry axis corresponds to a rotational symmetry with not just one radius but a rotation between a first and a second radius yielding an overall ellipsoidal characteristic when viewed in a cross-section substantially perpendicular to the symmetry line14-0.

As before a magnetization of higher order symmetry, rotational symmetry, or ellipsoidal symmetry within a cross-section shall still be considered symmetrical to the higher order symmetry, rotational symmetry, or ellipsoidal symmetry, even if only 90%, 80% or 50% of the cross-sectional area in fact exhibit a magnetization of higher symmetry with regards to the symmetry line14-0. Similarly, the magnetization of the back-bias magnet shall be considered of higher order symmetry, rotational symmetry, or ellipsoidal symmetry, even if only 90%, 80% or 50% of the volume of the magnet in fact exhibit a magnetization of higher symmetry with regards to the symmetry line14-0.

It will be noted that at a lower portion of the cross-sectional view (lower or zero z values) the magnetization of themagnet400 is almost completely aligned along the z axis. With increasing z coordinate however the magnetization is increasingly inhomogeneous. This is to say the higher the z coordinate the larger is an angle α between the z direction and the orientation of the magnetization as may be seen fromFIG. 14A when comparing the angle α for increasing z coordinates. Obviously the magnetization is aligned parallel along the symmetry axis140-0. When walking parallel to the symmetry line14-0 but not on the symmetry line, which would be in the z direction for a given x coordinate, the angle α will substantially increase with increasing z values. Such a behavior may be referred to as monotonic, more precisely monotonically increasing.

If one was to walk along a path perpendicular to the symmetry line14-0 one may experience a non-monotonic behavior of the angle α. This is to say when walking parallel to the symmetry line14-0, the angle α may first decrease until the symmetry line14-0 is reached and will increase again after having passed the symmetry line. Walking perpendicular to the symmetry line14-0 would correspond inFIG. 14A to walking in x direction for a given z value along the cross section.

Likewise, the angle α of the magnetization increases when walking away from the symmetry line in a horizontal direction (constant z coordinate) for those portions of themagnet400 that are not at the lower part ofFIG. 14. The increasingly inhomogeneous magnetization is best seen when comparing the angle α for arrows14-1,14-2, and14-3. An alternative way of describing the increasingly inhomogeneous magnetization when walking along the z direction (except along the symmetry line14-0) is to call it increasingly divergent. It will be appreciated that the cross-sectional distribution of magnetization serves for illustrative purposes, only and not to limit the teaching of the present disclosure in any way.

A person of ordinary skill will appreciate that it is feasible to produce a bulk magnet comprising an inhomogeneous magnetization as illustrated inFIG. 14A using a mold process. According to a first variant of such molding process, and somewhat similar to the discussion with regards to a production of radially magnetized magnets (FIG. 3a, 3brespectively), the molding tool may be configured to generate a spatially varying magnetic flux density inside the tool while magnetizable molding material is injected into and/or melted inside the molding tool. The spatially varying magnetic flux density inside the molding tool will project onto the magnetizable molding material and shall persist once the molding process is completed yielding thebulk magnet400 with inhomogeneous magnetization as a unitary member. In fact molding tool, magnetizable molding material and spatially varying magnetic flux density inside the tool may be selected to virtually achieve any desired spatially varying magnetic flux density inside themagnet400 once the molding process is finished.

It will be appreciated that an alternative molding process may be used to produce a bulk magnet comprising an inhomogeneous magnetization as illustrated inFIG. 14A. The molding tool may be filled with a standard magnetizable or magnetic molding material and may harden in the desired form of the inhomogeneous magnet to be produced. It is conceivable that during the hardening of the inhomogeneous magnet to be produced no external magnetic field or a homogeneous external magnetic field may be applied. This would lead to a magnet showing a moreless vanishing magnetization or a uniform magnetization. Once the magnetizable molding material is hardened, an inhomogeneous external magnetic field may be applied to the hardened molding material in the shape of the inhomogeneous magnet to be produced. It may be of advantage to apply the inhomogeneous magnetic field to the hardened molding material while it is still in the molding tool. Such an approach may be of advantage as theinhomogeneous magnet400 leaves the molding tool. As a trade-off time required per unit inside the molding tool may be increased with this approach. Depending on circumstances it may however be of interest to move the hardened molding material in the shape of the inhomogeneous magnet into a magnetization device providing a sufficiently large inhomogeneous magnetic field to project onto the magnetizable hardened molding material in the shape of the inhomogeneous magnet; thereby completing manufacture of theinhomogeneous magnet400 according to the present disclosure.

FIG. 14B illustrates an exemplary shape of theinhomogeneous magnet400 according to the present disclosure. It may be convenient to provide themagnet400 in a brick-type, i.e. cuboidal shape or slightly tapered brick-type shape, as displayed inFIG. 14B. Such a shape may be of interest in order to replace known back-bias magnets with theinhomogeneous magnet400 being moldable. A back-bias magnet supplier would typically overmold the back-bias magnet400 and the sensor arrangement120 (not shown) in order to build a module that is sold on to a client of the supplier, the module now comprising communication means from the sensor elements to an ECU, which are not discussed with regards to this disclosure in detail.

Without limitation the sensor100 (seeFIG. 2) built by the automotive supplier may as well have a brick-type shape as shown inFIG. 14B, while communication means form the sensor elements to the ECU are not shown. Thesensor100, too may have a shape of rotational symmetry or ellipsoidal symmetry. Thesensor100 of the rotational or ellipsoidal symmetry may optionally take a frustum shape, depending on circumstances. A person of ordinary skill will understand that an ellipsoidal shape of thesensor100 may have the advantage that a rotation of thesensor100 upon installation is easily prevented just by some housing provided within the vehicle matching the ellipsoidal shape and thereby arranging thesensor100 in an intended position.

If thesensor100 was however of a rotational symmetry one may provide a groove or a notch at a face of the sensor in order to provide an arranging of the sensor as is achievable for the ellipsoidal shape. It may be of advantage to arrange the groove or notch away from the magnetic-field sensor arrangement120, in order for the groove or notch not to affect a magnetic field distribution close to the magnetic-field sensor arrangement120 (not shown).

FIG. 14C illustrates such a shape for thesensor100 comprising agroove101 away from thesensing elements190. Such a notch may mate with a protrusion within the housing for thesensor100 provided in a device using the sensor, such as a vehicle. As an alternative to the notch, a frustum shapedsensor100 may comprise non-parallel top and bottom faces (more generally speaking non-parallel non-circumferential faces) so that thesensor100 will only mate with a corresponding housing in a defined circumferential position. Other options of positioning thesensor100 of rotational symmetry within the corresponding housing will be apparent to person of ordinary skill in the art and shall therefore not be explained any further here.

FIG. 14C discloses a further alternative of implementing thesensor100. In the implementation ofFIG. 2 thesensor elements190 are arranged in a sensor package forming the magnetic-field sensor arrangement120. Unlike inFIG. 2, thesensor100 ofFIG. 14C does not comprise the package forming the magnetic-field sensor arrangement120. It will be noted that one packing/molding step may be spared by implementing thesensor100 using a bare-die chip195 carrying thesensor elements190 without the package. Such an implementation of thesensor100 will be more cost-efficient for the (automotive) supplier. As a trade-off care needs to be taken that thesensing elements190 and consequently the bare-die chip195 are spatially correctly arranged with regards to the back-bias magnet400. While their correct alignment in the previous implementations of thesensor100 was catered for by the chip manufacturer, the correct alignment would now be a task left to the supplier.

While there is a spatial distance between the bare-die chip195 and the back-bias magnet400 inFIG. 14C, it will be appreciated, that the inhomogeneous magnetization of the back-bias magnet400 may be designed such that the bare-die chip195 can be directly placed onto the back-bias magnet400. A person of ordinary art will appreciate that the bare-die chip195 typically requires some coupling means in order to provide an electrical communication from the bare-die chip195 to an outside thereof. Such means of providing electrical communication may be in the form of a lead frame, but are not limited thereto. A person of ordinary skill will appreciate other options for providing the electrical communication, which are not limiting the teaching of the present disclosure and are therefore not described in further detail. For the remainder of the present disclosure bare-die chip195 shall be construed as optionally comprising the coupling means. In various embodiments, the bare-die chip195 design of the back-bias magnet400 facilitates the correct spatial arrangement of the bare-die chip195 relative to the back-bias magnet400.

FIG. 14D illustrates a further alternative of implementing thesensor100 comprising the back-bias magnet400. In fact, for the implementation ofFIG. 14D, theinhomogeneous magnet400 also serves as the housing of thesensor100. By appropriately controlling both spatial distribution of the inhomogeneous magnetization of themagnet400 and the positioning of thebare die chip195 relative to the inhomogeneous magnetization, the package covering thesensing elements190 and the further molding material providing the housing may be spared. InFIG. 14D the spatial distribution of magnetization is substantially symmetrical to the symmetry line14-0, showing different degrees of inhomogeneity14-1,14-2,14-3 pertaining to the angle α as was explained with regards toFIG. 14A.

It will be appreciated that theinhomogeneous magnet400 is of advantage when used together with a magnetic-field sensor arrangement120 as less magnetic material is required in order to achieve a comparable inhomogeneous magnetic flux density at thesensor elements190. This is due to the fact that the magnet400 (seeFIG. 14A, C, D) may be arranged closer to magnetic-field sensor arrangement120, wherein say first and second sensor elements190-1,190-2 (seeFIG. 2, 14C, 14D) are placed, than for magnet arrangements not having a convex shape as themagnet400.

As a further benefit of themagnet400 thesensor100 and/or themagnet400 require less space than would those systems comprising non-convex magnets (such as forexample magnet150 ofFIG. 1A,magnet110 ofFIG. 3A, 3B, 6A, or6B). In spatially constrained environments such as motor space of a combustion engine in the automotive arena smaller size of the back-bias sensor system is of interest.

It is to be noted that a moving target wheel rotating indirection220 is shown for illustrative purposes only inFIGS. 14C and 14D and does not form part of the described (back-bias)sensor100.

It will be appreciated by a person of ordinary skill in the art that theinhomogeneous magnet400 may be formed using hard ferrite material or rare earth materials as magnetizable molding material, such as ferrites, aluminum-nickel-cobalt (AlNiCo), or samarium-cobalt (SmCo) or neodymium-iron-boron (NdFeB), to name some non-limiting examples, respectively.

Generally, hard ferrite magnets are cheaper than rare-earth based magnets which as such would reduce magnet costs, however hard ferrite magnets have a weaker magnetic moment therefore will produce a weaker homogeneous magnetic fields for homogeneous magnets of identical size when compared to rare-earth based magnets. In order to compensate for this tradeoff, the use of inhomogeneous hard ferrite magnets according to the present disclosure helps increasing their respective magnetic field matching the magnetic field strength of rear earth magnets at the cost-benefit of hard ferrite magnets. In the pasta rare earth magnets were conveniently used for the non-convex magnets described above (see forexample magnet150 ofFIG. 1A,magnet110 ofFIG. 3A, 3B, 6A, or6B). Therefore theinhomogeneous magnet400 employing hard ferrite materials comes with further advantage over non-convex magnets made of rare earth magnet materials, such as samarium-cobalt (SmCo) or neodymium-iron-boron (NdFeB).

FIG. 15 schematically illustrates the B_xcomponent relative to the symmetry line of a magnet (x=0) for a given y coordinate. In this respect the illustration ofFIG. 15 somewhat corresponds to the scenario depicted inFIG. 5 as explained above. It becomes apparent that while the B_xcomponent for an homogeneous magnet (see solid line15-3) is of odd symmetry with regards to x=0, the B_xcomponent for an inhomogeneous magnet (saymagnet400 as discussed above) is almost vanishing over a substantial range of x-coordinates, as can be seen from the long dashed line15-4. The short dashed lines15-1 and15-2 indicate typical positions for magnetoresistive sensors, such as GMR sensing elements.

As discussed before with regards to curve270-6 (seeFIG. 5), the B_xcomponent of theinhomogeneous magnet400 shows an increased linear range and would therefore represent a preferred position for GMR sensor elements. The magnetic-field sensor elements190 (i.e.FIG. 2) could conveniently be positioned symmetrically about x=0 as indicated by position lines15-1,15-2, respectively, over a wider x range than for the homogenous magnet (see line15-3 ofFIG. 15). InFIG. 15 for the simulated magnetic field components for the homogeneous and inhomogeneous magnet (see lines15-3 and15-4) a distance of the sensor plane with the sensor elements is 0.7 mm above the magnet in z direction. As indicated the sensor elements show a sensor pitch or distance of 2.5 mm in x direction.

FIG. 16 illustrates a 3D plot of an exemplary simulation of magnetization for theinhomogeneous magnet400 ofFIG. 14 using a standard polymer-bound hard ferrite molding material. These molding materials typically show a remanence magnetic field of about 270-280 mT, and a corresponding coercitivity of 180 kA/m. As can be clearly seen a spatial distribution of the magnetization within themagnet400 is inhomogeneous, as was already schematically discussed with regards toFIG. 14A. The color coding as indicated on the scale to the right ofFIG. 16 illustrates a strength and direction of magnetization. It will be appreciated the magnetization of the inhomogeneous (back-bias)magnet400 will provoke a magnetic flux density outside themagnet400, different to so called Halbach magnet arrangements which represent magnet configurations with virtually all magnetic flux density confined inside the Halbach magnet. Such a confinement of magnetic flux to the inside of the magnet, would with non-Halbach magnets be achievable, if the magnet would be infinitely long, high, and/or wide. Also fromFIG. 16, a person of ordinary skill in the art will readily appreciate that virtually any desired inhomogeneous distribution of magnetization within themagnet400 may be generated, as was explained already above.

FIG. 17 illustrates further details taken from the simulation ofFIG. 16. Displayed is the simulated B_xcomponent in mT of the magnetic field produced by themagnet400 centered at the symmetry line (see14-0 ofFIG. 14) for realistic distances of the sensor elements from the surface of themagnet400 in y and z direction, respectively. The assumed distances are 0.7 mm in z direction and a central placement in y-direction (y=0 mm).

Line17-1 illustrates the B_xcomponent for a substantially homogeneous magnet, while lines17-2,17-3, and17-4 show the B_xcomponent for an increasinglyinhomogeneous magnet400. The increasing inhomogeneity shown for lines17-2,17-3, and17-4 may be represented by an increasing angle α (seeFIG. 14) associated with line14-0 to14-1,14-2, and14-3. As already discussed forFIG. 15 the increasingly inhomogeneous magnetization as shown inFIG. 17 for lines17-2,17-3, and17-4, increases a linear range of the magnetoresistive sensor elements190 (not shown) to be placed in x direction as indicated by the dotted lines15-1,15-2, respectively.

As the B_xcomponent for the strongest inhomogeneity represented by line17-4, almost vanishes at the sensor positions15-1,15-2, respectively, this amount of inhomogeneity of the B_xcomponent would make the sensor positions15-1, and15-2 ideal positions for placing the sensor elements in the x direction, as was described before with regards toFIG. 5.

It will be appreciated by a person of ordinary skill in the art that the present disclosure depicts inhomogeneous magnetization of the magnet400 (seeFIG. 1A, 1B, 3A, 3B, 4-14, 14A, 14D, 15-17) within cross-sections of the inhomogeneous magnet, such as the xy or xz plane, only, for illustrative purposes. The inhomogeneous magnet of the present disclosure is however in no ways limited to such a scenario. The magnet may therefore comprise further inhomogeneous magnetization contributions within further cross-sections of the magnet, the further cross-sections being perpendicular to those depicted in the Figures of the present disclosure.

Depending on the conditions, embodiments of the inventive methods may be implemented in hardware or in software. Implementation may be performed on a digital storage medium, in particular a disk, CD or DVD comprising electronically readable control signals which may cooperate with a programmable computer system such that an embodiment of an inventive method is performed. Generally, an embodiment of the present invention thus also consists in a software program product, or a computer program product, or a program product, comprising a program code, stored on a machine-readable carrier, for performing an embodiment of an inventive method, when the software program product runs on a computer or a processor. In other words, an embodiment of the present application may thus be realized as a computer program, or a software program, or a program comprising a program code for performing an embodiment of a method, when the program runs on a processor. The processor may be formed by a computer, a chip card (smart card), a central processor (CPU=central processing unit), an application-specific integrated circuit (ASIC), or any other integrated circuit, respectively.

Computer programs, software programs or programs may be employed, for example, in the context of the manufacturing process, i.e., for example, for controlling the manufacture of respective embodiments of magnetic-field sensors. Respective programs may thus be employed and used in the context of manufacturing plants for controlling same, but also in the context of designing and in the context of laying out respective embodiments of magnetic-field sensors. As the above listing has already shown, processors are not to be understood in the sense of classical computer processors only, but also in the sense of application-specific processors as occur, for example, in the context of machine tools and other production-relevant installations.

While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations and equivalents as fall within the true spirit and scope of the present invention.

Claims (20)

What is claimed is:

1. A magnetic-field sensor comprising:

a magnetic-field sensor arrangement; and

a back-bias magnet, wherein a structure of the back-bias magnet comprises an inhomogeneous magnetization.

2. The magnetic-field sensor as claimed inclaim 1, wherein the back-bias magnet is moldable as unitary member and of cuboidal shape, circular shape, elliptical, or frustum shape.

3. The magnetic-field sensor as claimed inclaim 2, wherein the back-bias magnet comprises materials selected from the group consisting of ferrites, aluminum-nickel-cobalt (AlNiCo), samarium-cobalt (SmCo) and neodymium-iron-boron (NdFeB).

4. The magnetic-field sensor as claimed inclaim 1, wherein the inhomogeneous magnetization of the back-bias magnet is symmetrical to a first symmetry line within at least one cross-section of the back-bias magnet.

5. The magnetic-field sensor as claimed inclaim 4, wherein the first symmetry line is a symmetry line of a substantially mirror-symmetrical inhomogeneous magnetization within the at least one cross-section of the back-bias magnet.

6. The magnetic-field sensor as claimed inclaim 4, wherein the first symmetry line within the at least one cross-section of the back-bias magnet is a symmetry line of higher order, rotational symmetry, or ellipsoidal symmetry.

7. The magnetic-field sensor as claimed inclaim 4, wherein the inhomogeneous magnetization is further symmetrical to the first symmetry line within a further cross-section of the back-bias magnet, the further cross-section intersecting the cross-section at the first symmetry line.

8. The magnetic-field sensor as claimed inclaim 1, wherein the inhomogeneous magnetization of the back-bias magnet causes a magnetic flux density outside the back-bias magnet.

9. The magnetic-field sensor as claimed inclaim 3, wherein magnetic flux caused by the inhomogeneous magnetization is substantially not confined to an inside of the back-bias magnet.

10. The magnetic-field sensor as claimed inclaim 1, wherein the back-bias magnet comprises the inhomogeneous magnetization in at least 50% of a volume of the back-bias magnet.

11. The magnetic-field sensor as claimed inclaim 4,

wherein the at least one cross-section is spanned by a first direction and a second direction, the first and second direction not being parallel, and

wherein when walking along the second direction for a given coordinate value for the first direction, an angle between the second direction and a local direction of magnetization varies at least over a portion of a walking path, the walking path being different from the first symmetry line.

12. The magnetic-field sensor as claimed inclaim 11, wherein the angle varies monotonically when walking along the walking path.

13. The magnetic-field sensor as claimed inclaim 11, wherein the angle varies non-monotonically when walking along the walking path, if the walking path runs perpendicular to the first symmetry line.

14. The magnetic-field sensor as claimed inclaim 1, wherein the magnetic-field sensor arrangement comprises a first magnetic-field sensor element and a second magnetic-field sensor element, the first magnetic-field sensor element being arranged, with respect to the back-bias magnet, such that the first magnetic-field sensor element is exposed, with regard to a predetermined spatial direction, to a magnetic flux density caused by the back-bias magnet and being within a first flux density range, and the second magnetic-field sensor element being arranged, with respect to the back-bias magnet, such that the second magnetic-field sensor element is exposed, with regard to the predetermined spatial direction, to a magnetic flux density caused by the back-bias magnet and being within a second flux density range.

15. The magnetic-field sensor as claimed inclaim 14, wherein the first flux density range and the second flux density range enable operation of the first and second magnetic-field sensor elements.

16. The magnetic-field sensor as claimed inclaim 14, wherein the first and second flux density ranges only comprise values smaller than or equal to 20 mT in magnitude.

17. The magnetic-field sensor as claimed inclaim 14, wherein the first flux density range comprises flux densities of opposite sign to the second flux density range.

18. The magnetic-field sensor as claimed inclaim 15, wherein the first and second magnetic-field sensor elements are magneto-resistive sensor elements.

19. The magnetic-field sensor as claimed inclaim 15, wherein the first and second magnetic-field sensor elements are arranged on a substrate, and wherein the predetermined spatial direction is substantially parallel to a main surface of the substrate.

20. The magnetic-field sensor as claimed inclaim 1, wherein the back-bias magnet is annular or comprises an annular section.

Images